Before the dinosaurs appeared, this Triassic "King of Lizards" ruled Antarctica.

Antarctanax Shacletoni hunts down an insect on the river bank in Antarctica during the early Triassic.

Credit: Adrian Stroup’s Copyright / Field Museum

Millions of years before the earth shook from the steps T. Rex – the so-called "king of the dinosaurs" – forest Antarctica was home to the "king of lizards" the size of an iguana.

This ancient reptile was an archosaur – part of the same group that later included dinosaurs, pterosaurs and crocodiles. Scientists have recently discovered a partial lizard skeleton that existed 250 million years ago, at a time when Antarctica was full of the life of plants and animals.

Scientists reported in a new study that not only the fossil of this former “king” provides a clearer picture of the forest landscape of ancient Antarctica, but also helps explain the evolutionary landscape after the largest mass extinction in Earth’s history. [Antarctica: The Ice-Covered Bottom of the World (Photos)] Although the lizard fossil was incomplete, the researchers were able to determine from the fused vertebrae that the animal was an adult reptile, and it probably had a length of 4 to 5 feet (1.2 to 1.5 meters). They dubbed it Antarctanaxshackletoni: The first part of its name comes from the Greek words “king of Antarctica”; The second part is a tribute to the discoverer of the British polar explorer Ernest Shackleton, who called the Birdmore Glacier, where there are many fossils in the Antarctic, including AntarctanaxRecently found after the 1908 expedition.

Thin features in the bones of the spine and the feet of the lizard indicated that it was a new species, and its shape suggested that it lives on the ground, running on forest soil, lead study author Brandon Pikuk, postdoctoral student at the Museum of Natural History in Chicago told Meeker Live Science.

“He has no fixtures in his legs that would make us think that he lived in trees or that this is a burrowing hole,” said Pikuk.

The side of one of the blocks holding Antarctanax Shacletoni; he retains several vertebrae, ribs and right leg.

Credit: Copyright Brandon Pikuk / Field Museum

"Widespread forests"

These trees may be difficult to imagine if we imagine Antarctica as it is today: a frozen, mostly lifeless, ice-covered desert. But hundreds of millions of years ago in Antarctica there was a warm humid environment, where the temperature rarely, if ever, dropped below zero, the study authors report.

“We have evidence that forests are widespread, and large rivers flow through these forests,” said Pikuk. Among the trees and rivers, amphibians roamed, relatives of mammals called cynodonts, other mammal-like predators called dicynodonts, who had fangs and beaks, and reptiles like Antarctanaxhe added.

But this fossil also contributes to an important evolutionary history. With the discovery of this previously unknown ancient reptile, researchers are bringing together an unexpected variety of archosaurs that arose soon after the mass extinction in Perm – a catastrophic event about 252 million years ago, which destroyed about 96 percent of all marine species and about 70 percent of terrestrial vertebrates. Scientists previously thought that after this global extinction, it took many millions of years for animals to diversify and fill the empty niches of the planet. But Antarctanax According to the study, archaurus began diversification just a couple of million years after the disappearance of the Permian.

“If you look at the earliest breeds of the Triassic, archosaurs and other groups emit explosive,” said Pikuk in an interview with Live Science. While AntarctanaxA iguana-like body may not seem particularly dramatic, some Triassic reptiles evolved to float like pterosaurs, while others returned to the seas and eventually turned into huge ichthyosaurs and plesiosaurs – and their ancestors probably appeared at the same time Antarctanaxhe explained.

"Existence Antarctanax the early triassic implies that all these other crazy pedigrees must have already existed at this stage, even if we do not have good fossils during this time, ”said Pikuk.

The results were published online (January 31) in the journal Vertebrate Paleontology.